The present invention relates to a method and a device for treating the substrate of an integrated circuit or similar product during manufacture, the purpose of said treatment being at least to remove, using the action of at least one treatment liquid, unwanted particles borne by a face to be treated of said substrate.
Such unwanted particles may include dust or similar particles, or even portions of unhardened photosensitive resin following exposure of the substrate through a mask. Consequently, said treatment liquid may be a washing or rinsing liquid (for example water) or even a liquid for curing said resin.
Many methods and devices for such a treatment are already known. Among these known methods and devices, those described in document U.S. Pat. No. 4,655,162 propose holding said substrate, during said treatment, so that its surface to be treated is directed downward. This results in the advantage that said unwanted particles are easily removed, since they are subjected to the effects of gravity in addition to the dragging effect of said treatment liquid. In this earlier document, said treatment liquid is contained in a small dish, which is placed under said substrate, and into which the latter can be introduced.
The subject of the present invention is a method and a device of this type, in which the removal of said unwanted particles is further improved.
To this end, according to the invention, the method for treating the substrate of an integrated circuit or similar product during manufacture, the aim of said treatment being at least to remove, using the action of at least one treatment liquid, unwanted particles borne by a face to be treated of said substrate and said substrate being held, during said treatment, so that said face to be treated is directed downward, is noteworthy:
in that said treatment liquid is sprayed from the bottom upward over said face to be treated; and
in that ultrasound waves are applied to said treatment liquid, which transmits said waves upto said substrate.
Thus, by means of such a method, said unwanted particles are completely taken away from said face to be treated by ultrasound, before being removed by the joint effect of the liquid drag and gravitational attraction. The result thereof is a particularly efficient removal, since, by virtue of the ultrasound, no particle is able to remain sufficiently strongly attached to said face to be treated so as to resist the liquid and gravity.
According to a first embodiment, said sprayed treatment liquid forms a plurality of individual jets, transmitting said ultrasound waves to said substrate. As a variant, said sprayed treatment liquid may form a liquid layer which covers said face to be treated and which transmits ultrasound waves to said substrate.
During said treatment, said substrate could be immobile. However, it is often preferable that it is made to rotate about a vertical axis. Such a rotational movement may be continuous or alternating.
To implement such a method, the present invention in addition relates to a device which is noteworthy in that it comprises:
means for holding said substrate such that said face to be treated is directed downward;
a working surface directed upward and placed under said substrate, facing the latter;
means for spraying the treatment liquid, mechanically connected to said working surface; and
at least one ultrasound transducer, mechanically connected to said working surface.
Preferably, said working surface rests on a tank for a heat-conducting liquid and said ultrasound transducer is attached to said tank. Said heat-conducting liquid, which may flow through said tank, thus makes it possible to absorb and remove the heat released by said transducer.
Moreover, it is advantageous that said means for spraying the treatment liquid are in thermal contact with said heat-conducting liquid in the tank. Thus, by heat exchange with the latter, the said sprayed treatment liquid may be brought to a suitable operating temperature. Of course, to this end, it is possible to provide an auxiliary heating source for said liquid in a tank, where the heat supplied by the ultrasound transducer would not be enough for the treatment liquid to reach this operating temperature.
To drain said sprayed treatment liquid after its impact on said face to be treated, it is advantageous to provide a drainage channel at the periphery of said working surface. An annular deflector surrounding said working surface and projecting upward therefrom, intended to direct the spray of said treatment liquid toward said channel may be combined with this channel. A deflector of this sort is particularly advantageous when said substrate rotates during spraying and when the treatment liquid is ejected at the periphery of said substrate. It will be noted that said working surface and said projecting annular deflector form a sort of bowl inside which said substrate may be at least partially placed during spraying. Where, in this bowl, the substrate is relatively far from the working surface, the liquid spray jets remain individual. On the other hand, if the substrate is relatively close to the working surface, said jets may form, by means of the surface tension effect, a liquid layer covering and joining said working surface and said face to be treated of the substrate.
Preferably, said means for holding said substrate are free to move so that they can be moved away from said working surface, for example so that the working surface and said face to be treated of the substrate can be brushed or dried by blowing a gas thereon.
For the same reasons, it is advantageous for said deflector also to be mounted free to move so that it can be moved away from said working surface.